Manuel had left no truly viable successor after his death. Alexius II, his son, was still not in his teens and thoroughly spoiled and unfit for the post. Still, Alexius was made emperor anyway with Manuel's wife, Mary, assuming the regency. Because both were Latins, and everything Latin loathed by Byzantines, they were immediately unpopular and resistance to their rule quick in coming.
Enter Andronicus, a cousin of Manuel with imperial ambitions who had been banished to a remote castle for having the audacity to seduce Manuel's sister in law. Andronicus found himself surrounded by followers egging him onwards to Constantinople to claim the throne. He needed little encouragement. On his approach the armies deserted Alexius and his mother and the gates were thrown open to him to be received as their liberator.
If his new subjects welcomed him with open arms they soon regretted it. Andronicus had the boy emperor sign his mother's death warrant and then shot full of arrows and his corpse desecrated. And then he went on a killing spree that so shocked Byzantines and foreigners alike that it sparked a civil war and a foreign invasion by the Normans. Isaac, another Comnenus, survived an attempted execution and rallied enough supporters that a riot started and the mob took to the imperial palace to get the cruel emperor. He had wisely fled the scene but was caught, tortured at length and then stoned to death.
SB 1983, DOC IV 1 AU Hyperpyron Obv: The Virgin enthroned facing, nimbate, holding the head of the infant Christ before her; MHP QV to left and right.
Rev: AN–PONIKOC–ECPOTHC - Andronicus, holding labarum and globus cruciger, being crowned by Christ.
SB 1984, DOC IV 2a AU (Electrum) Aspron Trachy Obv: The Virgin standing facing, orans.
Rev: Andronicus standing facing, holding labarum and akakia, being crowned by Christ. 1183-1185 (Constantinople). $625 4/1/01.